Speech intelligibility means a percentage that a user comprehends a speech signal transferred from a sound system. For example, if the user hears that the sound system transfers 100 words, but comprehends only 50 words, the speech intelligibility of the system is 50%. As a portable mobile terminal gradually becomes miniaturized, maximum sound power that can be output by the mobile terminal gradually decreases. Accordingly, the speech intelligibility during communication of the user using the mobile terminal is affected. The speech intelligibility is an important indicator in measuring performance of the mobile terminal. Therefore, how the mobile terminal processes a speech signal to improve the speech intelligibility becomes the key to the development of the mobile terminal.
Currently, in a typical acoustic application scenario including a mobile terminal, a user, and a noise source, a to-be-speech signal is detected by using an automatic gain control algorithm, a small signal in the to-be-speech signal is amplified, the amplified signal is converted into an electrical signal, and the electrical signal is transferred to a speaker. After being amplified, the electrical signal transferred to the speaker reaches a maximum value allowed by the speaker. When the speaker works based on maximum output power, the speaker outputs a speech signal at a maximum output sound pressure level.
In the implementation process of the present disclosure, the inventor finds that the related technology has at least the following problems:
Usually, the average fluctuation amplitude of the speech signal is far less than the peak fluctuation amplitude. During excitation by a normal speech signal, when working normally, a speaker whose maximum rated output power is 1 watt has average output power that is generally only approximately 10% of the maximum rated output power (that is, 0.1 W). In a normal working state, if the amplitude of the electrical signal that is input to the speaker is further increased, a signal part having large amplitude in the speech signal causes the speaker overloaded, resulting in saturated distortion, and decreasing the speech intelligibility and articulation. In addition, if only the small signal in the speech signal is amplified, an effective dynamic range of the speech signal is narrowed. Accordingly, the speech intelligibility cannot be significantly improved, either.